This kind of hinge lid pack is disclosed in, for example, Japanese Patent Application KOKAI Publication No.2-296641 (U.S. Pat. No. 4,948,038). This known pack comprises a box-shaped body whose upper end is opened. A box-shaped lid is connected to a rear opening edge of the body through a self-hinge. The lid rotates around the self-hinge so as to cover an opening end of the body or to be detached from the opening end. In other words, the lid opens and closes the opening of the body.
The body has a shoulder on its front surface, and the shoulder extends along a front opening edge of the body. The lid has a flap on its front opening edge, which is folded into the lid.
According to the above-explained hinge lid pack, when the opening end of the body is covered with the lid, the flap of the lid first comes in contact with the shoulder of the body, and then is further folded into the lid. When the opening end of the body is completely covered with the lid, the flap of the lid goes beyond the shoulder, and its tip edge butts against a lower edge of the shoulder. In this lid closing state, since the flap of the lid and the shoulder of the body are engaged with each other, there is no case where the lid is opened accidentally.
Just after the flap goes beyond the shoulder, the flap springs back and clicks the front surface of the body, so that a click sound occurs. Therefore, a user can confirm that the lid is completely closed by the click sound. In the case of the above-explained hinge lid pack, the lid overcomes the engagement between the flap and the shoulder so as to be opened. At this time, the flap is largely turned back. Even if the lid is opened and closed repeatedly only a few times, an elastic force of the flap root is abruptly lowered. Thereafter, even if the lid is closed, a spring force of the flap is poor, and the flap cannot produce a clear click sound.
Also, since the engagement between the flap and the shoulder becomes poor, the lid might be opened accidentally.
Moreover, if the elastic force of the flap is decreased, the flap cannot return to the lid and remains exposed at the outside of the lid even if the rid is opened. In this case, the user must fold the flap into the lid before the lid is closed.